Known static mixers include a mixing conduit that defines a passage and a mixing element comprised of a series of mixing baffles disposed within the passage. When two or more fluids are pumped into the static mixer, the flow of fluid along and around the non-moving mixing baffles continuously blends the fluids. The flow of fluids eventually forms a relatively homogenous mixture upon exiting the static mixer. This method of mixing is very effective for viscous materials in particular, such as epoxies, acrylics, and polyurethanes.
Many variations of static mixers currently exist, including multiflux, helical, and x-lattice mixers, amongst others. In particular, mixing elements utilizing multiflux and helical designs are commonly formed from plastic and are disposable, as these designs can be injection molded to form a unitary multi-element structure. Multiflux mixing elements can statically mix two or more materials in a shorter length, with less retained waste, and with less back pressure than comparable helical mixers.
Currently, injection molded multiflux mixing elements are comprised of multiple mixing baffles connected by two or more sidewalls. The mixing baffles are generally comprised of one or more dividing panels for dividing the fluid flow, multiple deflecting panels positioned to move fluid in a direction offset from the direction of fluid flow, and one or more mixing panels for recombining the fluid flow. The sidewalls present in these mixing baffles provide structure and strength to the linked mixing baffles, thus allowing the mixing baffles to withstand elevated fluid pressures.
As fluid pressures within the static mixer increase, forces likewise increase on the mixing baffles within the passage. As a result, the mixing baffle at a position most downstream within the passage generally bears the total accumulated force exerted on the entire mixing element. Because of this, the most downstream element is the region of the static mixer most likely to fail during a mixing operation. To help prevent this, disposable multiflux mixing elements generally include sidewalls connecting the baffles to provide stability and additional support by transmitting forces from each individual baffle to the bearing surfaces of the mixer housing.
However, sidewalls present certain issues. For example, fluid trapped between a sidewall and an inner surface of the mixing conduit can exit the static mixer as unmixed streaks. Additionally, sidewalls can reduce the flow rate of fluid within a static mixer, thus impeding the mixing process. Further, the presence of sidewalls causes the static mixer to require a larger mixing conduit, thus requiring additional material to mold, which subsequently creates additional waste. Sidewalls also prevent certain baffle geometries and sizes from being molded with an injection molding process. Sidewalls function to block injection mold tooling from being able to access and core out certain desirable features and geometries. Further, sidewalls prevent small multiflux mixers from being manufactured. While helical mixing elements can be molded to have a diameter as low as 1.3 mm (0.050″), the smallest disposable multiflux mixers have a diameter that is almost four times larger. The walls of current multiflux mixing elements would occupy such a large portion of a static mixer's cross section at sizes smaller than 0.20″×0.20″ that the resulting multiflux mixer would be rendered ineffective. Additionally, any protruding teeth or ledges in the cavities of the multiflux mixing element would be too thin and fragile to withstand a fluid flow under pressure.
Therefore, there is a need for a static miser with a mixing element that does not require sidewalls.